Furthermore, am I (as a pedestrian) obliged to stop at pedestrian crossing red lights, or are they just a suggestion?
The highway code has plenty of advice for pedestrians, but little in the way of laws. There's
RTA section 25, Pedestrian Crossings that says
"A person who contravenes any regulations made under this section shall be guilty of an offence." but doesn't actually say what these regulations are other than
"The relevant authority may make regulations ..." So I don't know what to make of that.
Plus there are a number of other laws that can be summed up as "don't be a dick" around obstructing the highway, causing a nuisance, loitering and stuff that may apply.
But a pedestrian can choose to cross a road wherever they like* (unless it's a special no-pedestrians road like a motorway). You don't have to use a designated crossing. So if you don't fancy waiting for the green man at (say) a pelican you can always cross somewhere else, providing that you do so sensibly and don't fall foul of the "don't be a dick" laws.
Pedestrian crossings are a convenience to protect pedestrians from those causing the danger (drivers). It doesn't mean that peds at the crossing are treated in the same way legally as drivers.
* I do this every time I go to my local shop. There's a slightly inconveniently placed pelican. If the traffic is heavy then I detour and use the crossing but 90% of the time I just stroll across about 20m from the crossing. Taking care not to be a dick.